1. Technical Field
This invention relates to means for driving the threshing rotor of an agricultural harvester.
2. Prior Art
A self-propelled combine normally has a single internal combustion engine which powers both the traction wheels and the various components of the combine for processing the crop material to separate the seed or grain therefrom. In some combines, a gear-type change-speed transmission is utilized to drive the combine rotor. When the rotor jams, the gear transmission is shifted to a low output speed to supply greater torque to the rotor. In other prior art combines, the power train to the threshing rotor has included a variable speed belt drive whose speed ratio is adjustable, only while running, to change the rotational speed of the rotor. The variable speed belt drive utilizes driving and driven sheaves each having a pair of sheave halves which can be moved relative to one another to change their effective diameter. One of the sheaves is normally spring loaded toward its maximum effective diameter and the effective diameter of the other sheave is normally adjusted by power means such as a hydraulic actuator. When the sheaves are not rotating and the belt is not running, it is not possible to change the speed ratio of the variable speed belt drive. Thus, when the threshing rotor jammed, the variable speed belt drive could not be changed to a lower output speed to transmit more torque to the rotor and perhaps free the rotor.